The present invention relates to a ball joint bearing seat that envelops a ball head portion of a ball stud in such a way as to permit the ball head portion to slide therein.
Referring to FIGS. 8 and 9, a prior art ball joint typically has a plurality of load receiving ribs 44, 44 radially arranged on the outer surface of a bearing seat 43 that faces a bottom portion 42 of a housing 41. The bearing seat 43 and a ball head portion 45 of a ball stud are installed in the housing 41. The bearing seat 43 envelops the ball head portion 45 with the ends of the load receiving ribs 44, 44 in contact with the bottom portion 42. The load receiving ribs 44, 44 themselves are spaced apart from each other.
The load receiving ribs 44, 44 contact the housing 41 to enable smooth operation with stable operation torque by absorbing dimensional tolerances of the components. A load applied to the ball stud is supported by the load receiving ribs 44, 44. Flexure of the portions of bearing seat 43 located in between the receiving ribs 44, 44 releases support for the applied load. Thus, the above configuration gives the ball joint the ability to withstand loading and provides friction compensation.
However, when a heavy load is repeatedly applied to the ball stud of a ball joint that uses a bearing seat as shown in FIGS. 8 and 9, inevitable fatigue of the load receiving ribs 44, 44 causes the portions of the bearing seat 43 between the load receiving ribs 44, 44 to flex to a greater extent, thereby generating a great tensile stress on the inner surface of the bearing seat 43, i.e. the surface on which the bearing seat 43 contacts the ball head portion 45 of the ball stud. In the end, such stress may cause fatigue breakage of the bearing seat 43.